What is phylogeny?
The evolutionary history of organisms
What is a phylogenetic tree?
- A branching diagram that shows the relationships between species, often according to the time since a common ancestor
- For each species/group of species, shows which other species/group of species it shares its most recent common ancestor with
- Provides hypotheses of evolutionary relationship
What is anagenesis?
- When evolutionary changes accumulate slowly over time, a pattern of gradual phyletic change
- Does not increase biodiversity, is simply the gradual transformation of one species into another as its characteristics shift over time
- Depicted as a straight line on a phylogenetic tree
What is cladogenesis?
- An ancestral species undergoes speciation, producing two descendant species, both of which are distinct from their common ancestor
- Does increase biodiversity
- Depicted by a branching pattern on a phylogenetic tree
What is a phylogram?
A phylogenetic tree where the branch lengths represent the amount of inferred evolutionary change/time. (branching + evolutionary “time”)
What is a cladogram?
A phylogenetic tree where all branches are of equal length. (just branching)
What is a sister group?
- Two species (or groups of species) that share a common ancestor not shared by any other species or group
Character states can be similar for one of two reasons:
- Homologous characters (homologies): shared because of common ancestry, shared ancestral and derived characters
- Analogous characters (homoplasies): shared because of convergent evolution
What is homoplasy?
- Similarity in appearance but not in origin
What is homology?
the similarity of the structure, of organisms based upon their descent from a common evolutionary ancestor
How are homologies recognized?
- structural similarity
- relations between parts
- embryonic development
The strongest hypothesis of evolutionary relationships is:
the tree with the fewest number of changes required b/c it minimizes the total number of independent origins of characters states
What is the principle of parsimony?
The phylogeny requiring the fewest evolutionary changes is the best estimate of the true phylogeny = most parsimonious
Each nucleotide in the DNA sequence or amino acid sequence of proteins:
can act as a trait
What is the distance method?
- DNA sequence differences reflect time since the common ancestor (more time and difference = more distantly related)
- Can estimate degrees of relatedness from comparisons of DNA sequences
What is a monophyletic group?
Includes a common ancestor and all of its descendants
What is a paraphyletic group?
Includes a common ancestor and some, but not all, of its descendants
What is a polyphyletic group?
Does not include the common ancestor
What is adaptive radiation?
The rapid evolution of new species occupying new niches
What is graduated evolution?
- Slow and steady gradual evolution
- Results in anagenesis
What is punctuated evolution?
- Rare and rapid (on a geologic time scale) events of branching speciation
- Results in cladogenesis
